Adipose tissue vascularization: its role in chronic inflammation.

In obesity, the vascular complication is a result of insulin resistance, such as decreased capillary recruitment in skeletal muscle from endothelial insulin resistance. Recent progress in the study of obesity-associated inflammation suggests that vasculature dysfunction occurs in adipose tissue before insulin resistance. In obesity, capillary density and function fail to meet the demand of adipose tissue growth. The failure leads to microcirculation dysfunction from an impaired blood perfusion, which results in a local hypoxia response in adipose tissue. The hypoxia response in adipocytes and macrophages is a new cellular basis for the chronic inflammation. The obesity-associated inflammation has both positive and negative effects in the body. At the early stage, it amplifies the hypoxia signal to stimulate vasculature remodeling locally, and promotes systemic energy expenditure against obesity. At the late stage, it causes adipose tissue dysfunction for insulin resistance. These points suggest that in obesity, adipose tissue vascularization controls chronic inflammation and influences systemic insulin sensitivity.